1. Field of the Invention
The present invention relates to a webbing retractor in a seat belt system for restraining an occupant in a vehicle with a webbing belt.
2. Description of the Related Art
A webbing retractor constituting a main part of a so-called seat belt system for restraining an occupant in a vehicle with an elongated belt-shaped webbing belt basically comprises: a take-up shaft with which one end of the webbing belt is engaged; a frame for supporting the take-up shaft; and urging means such as a spiral coil spring or the like, for urging the take-up shaft in the direction of winding the webbing belt.
In addition to the above structure, an ordinary webbing retractor is provided with a lock device for locking the take-up shaft when a vehicle enters an abrupt deceleration state, to thereby resist a force of an occupant""s body, which moves toward the front of the vehicle due to inertia in the abrupt deceleration state, acting to pull out the webbing belt, and for improving the restraining force of the webbing belt; and a pretensioner for forcibly imparting rotation force in the take-up direction to the take-up shaft in the abrupt deceleration state of the vehicle.
Since the above-described conventional webbing retractor has a large number of parts to be used, the apparatus becomes large as a whole. Below is a detailed description of the above-described lock device and pretensioner.
The lock device ordinarily comprises a substantially circular V gear having ratchet teeth formed on the outer peripheral portion thereof. The V gear is mechanically connected to the take-up shaft via a torsion spring or the like, and follows the take-up shaft for rotation. A pair of lock plates are held by engagement on the side along the V gear and the take-up shaft, and when relative rotation is caused between the take-up shaft and the V gear, each lock plate moves outward in the radial direction of rotation of the take-up shaft. Each lock plate is formed with ratchet teeth, and when moved outward in the radial direction of rotation of the take-up shaft, meshes with the internal teeth of the ratchet hole formed in one of a pair of leg plates constituting a frame. Moreover, an acceleration sensor having an inertia ball is disposed in the direction that is outward in the radial direction with respect to the V gear (ordinarily, on the lower side). Due to the inertia ball rolling at the time of abrupt deceleration of the vehicle, an engagement pawl of the acceleration sensor engages with the ratchet teeth to restrict the rotation of the V gear. That is, during the abrupt deceleration state of the vehicle, the occupant""s body tends to move in the direction the vehicle is travelling due to inertia. At this time, the occupant""s body pulls out the webbing belt to rotate the take-up shaft. But since the V gear is locked by the engagement paw, a relative rotation is caused between the take-up shaft and the V gear, and each lock plate moves outward in the radial direction of rotation of the take-up shaft, and the ratchet teeth of each lock plate meshes with the internal teeth of the ratchet hole to restrict the rotation of the take-up shaft.
With such a conventional lock device, two (a pair of) lock plates are used to obtain mechanical strength sufficient for corresponding to rotation of the take-up shaft in the abrupt deceleration state of the vehicle, which is one factor leading to an increase in the number of parts.
On the other hand, the pretensioner comprises a pinion connected to one end of the take-up shaft via a one-way clutch, and a rack bar meshable with the pinion. The rack bar is formed integrally with a piston housed in a cylinder, moves with increase in the internal pressure of the cylinder to thereby mesh with the pinion and forcibly rotates the take-up shaft in the take-up direction via the one-way clutch. A gas generator is attached to the cylinder, which ignites a gas generating agent in the gas generator when an acceleration sensor other than the acceleration sensor of the above-described lock device detects the abrupt deceleration state of the vehicle to thereby generate gas instantaneously, and to move the piston by gas pressure.
The take-up shaft-side shaft portion of the above-described pinion or the pinion-side shaft portion of the one-way clutch is ordinarily rotatably supported by means of a bearing portion provided in the housing formed by a metal plate or the like, the bearing portion being brought into face contact with the outer peripheral face along the outer peripheral direction of the shaft portion. Therefore, for example, when the rack bar meshes with the pinion, the take-up shaft becomes eccentric, and in this state, when the take-up shaft is made to rotate, the take-up shaft rotates in the state of being pressed against the inner peripheral portion of the bearing. Hence, the friction resistance becomes large. By this friction resistance, the force by which the pretensioner forcibly rotates the take-up shaft via the rack bar and the pinion is converted into heat energy, hence the portion of the force actually leading to rotation of the take-up shaft decreases. Particularly, when synthetic resin material having a lower rigidity than the metal material forming the take-up shaft is used for the bearing portion so as to decrease the weight, an inner peripheral portion of the bearing portion is plastically deformed due to the above-described friction resistance. Hence, the inner peripheral face of the bearing portion becomes rough, to thereby further increase the friction resistance.
As described above, with the webbing retractor provided with a conventional pretensioner, the decrease of force rotating the take-up shaft of the pretensioner due to the friction resistance must be taken into consideration in advance, and the quantity of the gas to be generated should be increased for that amount. Therefore, the pretensioner is made large, and the webbing retractor increases in size accordingly.
In view of the above circumstances, it is an object of the present invention to obtain an inexpensive webbing retractor by making the pretensioner and the lock device small and reducing the number of parts.
To attain the above object, a first aspect of the present invention is a webbing retractor for use with a webbing belt having opposite ends, the webbing retractor comprising a cylindrical take-up shaft at which one end of a webbing belt is retained a lock device for restricting rotation of the take-up shaft in a direction for pulling out the webbing belt, during abrupt deceleration of a vehicle and a pretensioner for forcibly rotating the take-up shaft in the take-up direction opposite to the pulling-out direction during abrupt deceleration of the vehicle wherein the lock device includes a frame having a pair of leg plates opposite to each other along an axial direction of the take-up shaft, one of the pair of leg plates being formed with a ratchet hole whose inner peripheral portion serves as internal ratchet teeth, the leg plates having sides, a lock base provided coaxially and relatively rotatable with respect to the take-up shaft, in a vicinity of the one of the pair of leg plates a lock plate having external teeth meshable with the ratchet teeth, which is substantially integrally held by the lock base, and which restricts rotation of the lock base in the pulling-out direction by meshing of the external teeth with the ratchet teeth a torsion shaft having opposite ends, provided in the take-up shaft coaxially with the take-up shaft, one end of the torsion shaft being coupled to the take-up shaft, the other end being coupled to the lock base, for integrally rotating the take-up shaft and the lock base, and allowing rotation of the take-up shaft relative to the lock base due to torsion deformation of the torsion shaft, and a lock cover formed with a push nut portion with which a distal end portion of the torsion shaft is engaged, a hook portion with which the lock base is engaged, and an outer peripheral flange portion overlapping the frame, for pinching the one leg plate between one end portion of the take-up shaft and the lock cover and covering the lock base and the lock plate, and wherein the pretensioner includes a pinion provided coaxially with respect to the take-up shaft at the side of the other leg plate of the pair of leg plates and coupled directly or indirectly to the take-up shaft, a piston having an end portion, on which a rack bar meshable with the pinion is formed in an axial direction, a cylinder having a bottom portion and an end opening in an axial direction of the piston serves, for housing the piston and driving the piston with increase in internal pressure a gas generator for supplying gas between the bottom portion of the cylinder and the piston during abrupt deceleration of the vehicle a bearing portion facing an outer peripheral portion of a shaft portion provided coaxially with the pinion on the take-up shaft side of the pinion in a radial direction of the pinion, and having an inner peripheral portion such that a predetermined gap exists between the outer peripheral portion of the shaft portion and the inner peripheral portion, and a plurality of protrusions which are formed to protrude from one having a lower rigidity towards the other having a higher rigidity, of the inner peripheral portion of the bearing portion and the outer peripheral portion of the shaft portion, to thereby be brought into contact with the one having the higher rigidity, the webbing retractor further including an acceleration sensor for detecting a change in acceleration during abrupt deceleration of the vehicle, and for causing the external teeth of the lock plate to mesh with the internal ratchet teeth, upon detection of the change in acceleration and urging means provided at the side of the other leg plate of the frame, for urging the take-up shaft in the rotational direction for taking up the webbing belt.
A second aspect of the present invention is the webbing retractor according to the first aspect, wherein the pretensioner includes a cover for covering the pinion and the rack bar from a side opposite the other leg plate with respect to the pinion and the rack bar, the cover being formed with a bearing hole for pivotally supporting the pinion, a stopper facing the rack bar at the side in the driving direction of the piston due to increase in the internal pressure of the cylinder, and a restricting portion at the side opposite to the pinion with respect to the rack bar, wherein a peripheral portion of the bearing hole, the stopper and the restricting portion of the cover are formed of metal, and the remaining portion of the cover is formed of synthetic resin material.
A third aspect of the present invention is the webbing retractor according to the second aspect, wherein the protrusions are formed on the bearing portion, and the protrusions formed in a vicinity of a portion facing the shaft portion along a pressing direction of the rack bar against the pinion are more numerous in number than the protrusions formed in another portion of the bearing portion.
A fourth aspect of the present invention is the webbing retractor according to the third aspect, wherein the protrusions are brought into linear contact with one of the inner peripheral portion of the bearing portion and the outer peripheral portion of the shaft portion, with one of these being without the protrusions formed thereon.
A fifth aspect of the present invention is the webbing retractor according to the fourth aspect, wherein the lock device includes a V gear provided coaxially and relatively rotatable with respect to the lock base, meshing with the lock plate, which displaces the lock plate by relative rotation to thereby cause the external teeth to mesh with the ratchet teeth wherein the acceleration sensor includes an inertial mass body which moves due to change in acceleration during abrupt deceleration of the vehicle and a restriction member which is displaced according to movement of the inertial mass body and is engaged with the V gear due to the displacement, to thereby restrict rotation of the V gear.
A sixth aspect of the present invention is the webbing retractor according to the fifth aspect, wherein the urging means includes a spiral coil spring having opposite ends, with one end engaged directly or indirectly with the take-up shaft and the other end directly or indirectly engaged with the other leg plate of the frame, and urging the take-up shaft in a rotational direction for taking up the webbing belt due to rotation of the other end of the spring with respect to the one end of the spring in the direction of increasing the number of windings.
A seventh aspect of the present invention is the webbing retractor according to the second aspect, wherein the protrusion is formed in the bearing portion, in the opposite side of the rack bar with respect to the pinion, and on the inner peripheral portion of the bearing portion facing the outer peripheral portion of the shaft portion along the direction of the meshing face of the rack bar and the pinion.
An eighth aspect of the present invention is the webbing retractor according to the seventh aspect, wherein the protrusions are brought into linear contact with one of the inner peripheral portion of the bearing portion and the outer peripheral portion of the shaft portion, with one of these being without the protrusions formed thereon.
A ninth aspect of the present invention is the webbing retractor according to the eighth aspect, wherein the lock device includes a V gear provided coaxially and relatively rotatable with respect to the lock base, meshing with the lock plate, which displaces the lock plate by relative rotation to thereby cause the external teeth to mesh with the ratchet teeth; wherein the acceleration sensor includes an inertial mass body which moves due to change in acceleration during abrupt deceleration of the vehicle and a restriction member which is displaced according to movement of the inertial mass body and is engaged with the V gear due to the displacement, to thereby restrict rotation of the V gear.
A tenth aspect of the present invention is the webbing retractor according to the ninth aspect, wherein the urging means includes a spiral coil spring having opposite ends, with one end engaged directly or indirectly with the take-up shaft and the other end directly or indirectly engaged with the other leg plate of the frame, and urging the take-up shaft in a rotational direction for taking up the webbing belt due to rotation of the other end of the spring with respect to the one end of the spring in the direction of increasing the number of windings.
An eleventh aspect of the present invention is the webbing retractor according to the first aspect, wherein the protrusions are formed on the bearing portion, and the protrusions formed in a vicinity of a portion facing the shaft portion along a pressing direction of the rack bar against the pinion are more numerous in number than the protrusions formed in another portion of the bearing portion.
A twelfth aspect of the present invention is the webbing retractor according to the eleventh aspect, wherein the protrusions are brought into linear contact with one of the inner peripheral portion of the bearing portion and the outer peripheral portion of the shaft portion, with one of these being without the protrusions formed thereon.
A thirteenth aspect of the present invention is the webbing retractor according to the twelfth aspect, wherein the lock device includes a V gear provided coaxially and relatively rotatable with respect to the lock base, meshing with the lock plate, which displaces the lock plate by relative rotation to thereby cause the external teeth to mesh with the ratchet teeth wherein the acceleration sensor includes an inertial mass body which moves due to change in acceleration during abrupt deceleration of the vehicle and a restriction member which is displaced according to movement of the inertial mass body and is engaged with the V gear due to the displacement, to thereby restrict rotation of the V gear.
A fourteenth aspect of the present invention is the webbing retractor according to the thirteenth aspect, wherein the urging means includes a spiral coil spring having opposite ends, with one end engaged directly or indirectly with the take-up shaft and the other end directly or indirectly engaged with the other leg plate of the frame, and urging the take-up shaft in a rotational direction for taking up the webbing belt due to rotation of the other end of the spring with respect to the one end of the spring in the direction of increasing the number of windings.
A fifteenth aspect of the present invention is the webbing retractor according to the first aspect, wherein the protrusion is formed in the bearing portion, in the opposite side of the rack bar with respect to the pinion, and on the inner peripheral portion of the bearing portion facing the outer peripheral portion of the shaft portion along the direction of the meshing face of the rack bar and the pinion.
A sixteenth aspect of the present invention is the webbing retractor according to the fifteenth aspect, wherein the protrusions are brought into linear contact with one of the inner peripheral portion of the bearing portion and the outer peripheral portion of the shaft portion, with one of these being without the protrusions formed thereon.
A seventeenth aspect of the present invention is the webbing retractor according to the sixteenth aspect, wherein the lock device includes a V gear provided coaxially and relatively rotatable with respect to the lock base, meshing with the lock plate, which displaces the lock plate by relative rotation to thereby cause the external teeth to mesh with the ratchet teeth wherein the acceleration sensor includes an inertial mass body which moves due to change in acceleration during abrupt deceleration of the vehicle and a restriction member which is displaced according to movement of the inertial mass body and is engaged with the V gear due to the displacement, to thereby restrict rotation of the V gear.
An eighteenth aspect of the present invention is the webbing retractor according to the seventeenth aspect, wherein the urging means includes a spiral coil spring having opposite ends, with one end engaged directly or indirectly with the take-up shaft and the other end directly or indirectly engaged with the other leg plate of the frame, and urging the take-up shaft in a rotational direction for taking up the webbing belt due to rotation of the other end of the spring with respect to the one end of the spring in the direction of increasing the number of windings.
A nineteenth aspect of the present invention is the webbing retractor according to the first aspect, wherein the protrusions are brought into linear contact with one of the inner peripheral portion of the bearing portion and the outer peripheral portion of the shaft portion, with one of these being without the protrusions formed thereon.
A twentieth aspect of the present invention is the webbing retractor according to the nineteenth aspect, wherein the lock device includes a V gear provided coaxially and relatively rotatable with respect to the lock base, meshing with the lock plate, which displaces the lock plate by relative rotation to thereby cause the external teeth to mesh with the ratchet teeth wherein the acceleration sensor includes an inertial mass body which moves due to change in acceleration during abrupt deceleration of the vehicle and a restriction member which is displaced according to movement of the inertial mass body and is engaged with the V gear due to the displacement, to thereby restrict rotation of the V gear.
A twenty-first aspect of the present invention is the webbing retractor according to the twentieth aspect, wherein the urging means includes a spiral coil spring having opposite ends, with one end engaged directly or indirectly with the take-up shaft and the other end directly or indirectly engaged with the other leg plate of the frame, and urging the take-up shaft in a rotational direction for taking up the webbing belt due to rotation of the other end of the spring with respect to the one end of the spring in the direction of increasing the number of windings.
A twenty-second aspect of the present invention is the webbing retractor according to the first aspect, wherein the lock device includes a V gear provided coaxially and relatively rotatable with respect to the lock base, meshing with the lock plate, which displaces the lock plate by relative rotation to thereby cause the external teeth to mesh with the ratchet teeth wherein the acceleration sensor includes an inertial mass body which moves due to change in acceleration during abrupt deceleration of t he vehicle and a restriction member which is displaced according to movement of the inertial mass body and is engaged with the V gear due to the displacement, to thereby restrict rotation of the V gear.
A twenty-third aspect of the present invention is the webbing retractor according to the Twenty-second aspect, wherein the urging means includes a spiral coil spring having opposite ends, with one end engaged directly or indirectly with the take-up shaft and the other end directly or indirectly engaged with the other leg plate of the frame, and urging the take-up shaft in a rotational direction for taking up the webbing belt due to rotation of the other end of the spring with respect to the one end of the spring in the direction of increasing the number of windings.
A twenty-fourth aspect of the present invention is the webbing retractor according to the first aspect, wherein the urging means includes a spiral coil spring having opposite ends, with one end engaged directly or indirectly with the take-up shaft and the other end directly or indirectly engaged with the other leg plate of the frame, and urging the take-up shaft a rotational direction for taking up the webbing belt due to rotation of the other end of the spring with respect to the one end of the spring in the direction of increasing the number of windings.
According to the webbing retractor of the first aspect of the present invention, the take-up shaft and the lock base are connected via the torsion shaft, and the take-up shaft is urged in the direction of winding the webbing belt by means of the urging force of the urging means. By rotating the take-up shaft, the lock base and the torsion shaft are rotated integrally in the pulling-out direction opposite to the take-up direction against the urging force, and the webbing belt can be pulled out.
On the other hand, at the time of abrupt deceleration of the vehicle, the change in the acceleration (deceleration) at this time is detected by the acceleration sensor, and the lock device operates. That is, when the acceleration sensor detects a change in the acceleration (deceleration) at the time of abrupt deceleration of the vehicle, the acceleration sensor meshes the external teeth of the lock plate with the internal ratchet teeth formed on the one leg plate of the frame. Thereby, the rotation in the pulling-out direction of the lock base is resisted. At this time, the webbing tensioning force works as a rotation force on the torsion shaft via the take-up shaft in the pulling-out direction. Thereby, the torsion shaft is distorted, and the take-up shaft is rotated in the pulling-out direction of the webbing with respect to the lock base to pull out the webbing. Hence, an energy of tensioning the webbing is absorbed.
Here, since the distal end portion of the torsion shaft is engaged with the push nut of the lock cover, pulling out of the torsion shaft is prevented. Moreover, since the lock base is engaged with the lock cover by means of the hook portion, the lock plate held by the lock base is substantially covered with the lock cover. Thereby, rising of the lock plate is prevented. Furthermore, since the outer peripheral flange portion of the lock cover is superposed on the frame, dust and the like are prevented from coming into the mechanism.
Moreover, since the lock base and the lock plate are covered in a state in which the frame is put between the lock cover and the take-up shaft, the shaft portion comprising the lock base, the lock plate, the take-up shaft and the distal end portion of the torsion shaft is prevented from dropping out from the frame.
As described above, the webbing retractor according to the first aspect of the present invention can realize prevention of rising of the lock plate in order to resist the rotation in the direction of pulling out, the webbing, and prevention of the torsion shaft from coming off, which can absorb the energy at the time of resisting the pulling out of the webbing, by providing a single lock cover. Hence, the number of parts can be reduced and special processing of parts is not necessary. Moreover, dust and the like can be prevented from coming into the mechanism.
On the other hand, the pretensioner operates in the abrupt deceleration state of the vehicle described above. That is, at the time of abrupt deceleration state of the vehicle, the gas generator operates to supply gas to between the piston and the bottom portion of the cylinder, and the internal pressure of the cylinder rises due to this gas pressure to push out the piston. Thereby, the rack bar integral with the piston meshes with the pinion to thereby rotate the pinion. Hence, the take-up shaft is forcibly rotated in the take-up direction for taking up the webbing belt. Thereby, the force for restraining the occupant""s body by means of the webbing belt increases.
Here, in the present invention, the plurality of protrusions are formed projecting from the one having lower rigidity toward the other having higher rigidity, of the bearing portion or the shaft portion, along the rotation radius of the pinion, and the distal end portions of these protrusions are brought into contact with the one having the higher rigidity. That is, in the present invention, the shaft portion is pivotally supported by the bearing portion via the protrusions.
If an external force is applied to the shaft portion in the direction along the radial direction of the shaft portion in a state in which the shaft portion is rotating, the shaft portion becomes eccentric. Thereby, the gap between the inner peripheral portion of the bearing portion and the outer peripheral portion of the take-up shaft is narrowed in the above-mentioned displaced direction. At this time, the above-mentioned one having the higher rigidity tends to press the protrusions to deform them while relatively rotating toward the other having the lower rigidity. However, the portion of the protrusions contacting the one having the higher rigidity is extremely small compared to the area of the one having the higher rigidity on the side facing the one having the lower rigidity. Hence, the pressing force concentrates on the protrusions, and the protrusions are thereby easily plastically deformed. In this manner, since the protrusions are easily plastically deformed, the resistance of the protrusions against the rotation of the one having the higher rigidity becomes relatively small. Hence, even if the shaft portion becomes eccentric, the shaft portion can be smoothly rotated with little obstruction to the rotation of the shaft portion.
Moreover, since the inner peripheral portion of the bearing portion has a larger inner diameter than the outer peripheral portion of the shaft portion, there is a gap between the inner peripheral portion of the bearing portion and the outer peripheral portion of the shaft portion, on the sides of the protrusions along the rotational direction of the shaft portion. As described above, if the shaft portion is rotated in the eccentric state, the protrusions are plastically deformed. However, the plastically deformed portion of the protrusion is dragged toward the rotational direction due to the relative rotation of the one having the higher rigidity with respect to the one having the lower rigidity, and is settled in the above-mentioned gap. Therefore, the plastically deformed portions of the protrusions do not become an obstruction to the rotation of the shaft portion. In this sense, the shaft portion can be smoothly rotated, enabling the gas pressure supplied from the gas generator to be set to a small value. Thereby, the gas generator, the cylinder, the piston and the like can be made small, which contributes to the reduction in the size of the webbing retractor.
With the present invention, if the portion of the protrusions contacting the one having the higher rigidity is relatively extremely small compared to the area of the portion of the one having the higher rigidity facing the other having the lower rigidity, basically the above-described function is performed. Therefore, the contact state of the protrusion with respect to one having the higher rigidity maybe any of face contact, linear contact and point contact, but from the viewpoint that the smaller the contact portion, the better, linear contact is better than face contact.
According to the webbing retractor of the second aspect, by molding the cover with a synthetic resin material, the cover is made lightweight compared to the case where the cover is molded with a metal material, which contributes to making the webbing retractor lightweight. Of the cover, however, the peripheral portion of the bearing hole for pivotally supporting the pinion, the stopper of a portion facing the rack bar along the moving direction of the piston pushed out from the cylinder, and the restricting portion at the opposite side of the pinion with respect to the rack bar are formed with a metal. Hence, these portions have higher strength than the other portions. Therefore, sufficient strength against friction, impact and pressing force can be secured, when the pinion rotates, when the piston is pushed out from the cylinder to bring the rack bar into contact with the stopper, and when the rack bar is displaced toward the opposite side of the pinion and brought into contact with the restricting portion by means of the reaction force from the pinion when the rack bar meshes with the pinion.
According to the webbing retractor of the third aspect, the number of the protrusions formed in the vicinity of the portion facing the shaft portion along the pressing direction of the rack bar against the pinion is greater than the number of the protrusions formed in the another portion.
The rack bar is to rotate the pinion by pressing the pinion teeth by means of the teeth of the rack bar. By means of the pressing force at this time, the pinion becomes eccentric along the pressing direction. Here, with the webbing retractor of the present invention, by forming protrusions as described above, the number of the protrusions formed is greater in the eccentric direction of the pinion. Therefore, when the pinion becomes eccentric, the outer peripheral portion thereof disposed on the inside of the bearing means presses the protrusions to plastically deform them.
According to the webbing retractor of the fourth aspect, since the protrusion is brought into linear contact with the side where the protrusion is not formed, the pressing force concentrates more effectively on the protrusion. Hence, the protrusion is plastically deformed more easily.
According to the webbing retractor of the fifth aspect, when the inertial mass body moves due to change in the acceleration in the abrupt deceleration state of the vehicle, the restriction member is displaced according to the movement of the inertial mass body to thereby restrict rotation of the V gear. If the lock base rotates in the state that the rotation of the V gear is restricted, relative rotation is caused between the V gear and the lock base, and the V gear displaces the lock plate due to the relative rotation, to thereby mesh the external teeth of the lock plate with the internal ratchet teeth. Thereby, the rotation of the lock base in the pulling-out direction is resisted. At this time, the webbing tensile force operates on the torsion shaft as a rotation force in the pulling-out direction via the take-up shaft. Thereby, the torsion shaft is distorted, and the take-up shaft is rotated in the direction for pulling out the webbing with respect to the lock base to thereby pull out the webbing. Hence, the energy is absorbed.
According to the webbing retractor of the sixth aspect, the urging means is the spiral coil spring. The one end of the spiral coil spring is engaged directly or indirectly with the take-up shaft, and the other end is directly or indirectly engaged with the other leg plate of the frame. When the take-up shaft is rotated in the pulling-out direction, the spiral coil spring is provided with increased number of winding, to thereby increase the restoring force. This restoring force becomes the urging force for urging the take-up shaft in the take-up direction.
According to the webbing retractor of the seventh aspect, the protrusions are formed in the opposite side of the rack bar with respect to the pinion, and on the inner peripheral portion of the bearing portion facing the outer peripheral portion of the shaft portion along the direction of the meshing face of the rack bar and the pinion.
The rack bar is to rotate the pinion by pressing the pinion teeth by means of the teeth of the rack bar, and the pressing force at this time operates in the direction of the meshing face between the rack bar and the pinion. Therefore, by forming the protrusions as described above, the number of the protrusions formed is greater in the eccentric direction of the pinion. Therefore, when the pinion becomes eccentric, the outer peripheral portion thereof arranged on the inside of the bearing means presses the protrusions to plastically deform them.
According to the webbing retractor of the eighth aspect, since the protrusion is brought into linear contact with the side where the protrusion is not formed, the pressing force concentrates more effectively on the protrusion. Hence, the protrusion is plastically deformed more easily.
According to the webbing retractor of the ninth aspect, when the inertial mass body moves due to change in the acceleration in the abrupt deceleration state of the vehicle, the restriction member is displaced according to the movement of the inertial mass body to thereby restrict rotation of the V gear. If the lock base rotates in the state that the rotation of the V gear is restricted, relative rotation is caused between the V gear and the lock base, and the V gear displaces the lock plate due to the relative rotation, to thereby mesh the external teeth of the lock plate with the internal ratchet teeth. Thereby, the rotation of the lock base in the pulling-out direction is resisted. At this time, the webbing tensile force operates on the torsion shaft as a rotation force in the pulling-out direction via the take-up shaft. Thereby, the torsion shaft is distorted, and the take-up shaft is rotated in the direction for pulling out the webbing with respect to the lock base to thereby pull out the webbing. Hence, the energy is absorbed.
According to the webbing retractor of the tenth aspect, the urging means is the spiral coil spring. The one end of the spiral coil spring is engaged directly or indirectly with the take-up shaft, and the other end is directly or indirectly engaged with the other leg plate of the frame. When the take-up shaft is rotated in the pulling-out direction, the spiral coil spring is provided with increased number of winding, to thereby increase the restoring force. This restoring force becomes the urging force for urging the take-up shaft in the take-up direction.
According to the webbing retractor of the eleventh aspect, the number of the protrusions formed in the vicinity of the portion facing the shaft portion along the pressing direction of the rack bar against the pinion is greater than the number of the protrusions formed in the another portion.
The rack bar is to rotate the pinion by pressing the pinion teeth by means of the teeth of the rack bar. By means of the pressing force at this time, the pinion becomes eccentric along the pressing direction. Here, with the webbing retractor of the present invention, by forming protrusions as described above, the number of the protrusions formed is greater in the eccentric direction of the pinion. Therefore, when the pinion becomes eccentric, the outer peripheral portion thereof disposed on the inside of the bearing means presses the protrusions to plastically deform them.
According to the webbing retractor of the twelfth aspect, since the protrusion is brought into linear contact with the side where the protrusion is not formed, the pressing force concentrates more effectively on the protrusion, hence the protrusion is plastically deformed more easily.
According to the webbing retractor of the thirteenth aspect, when the inertial mass body moves due to change in the acceleration in the abrupt deceleration state of the vehicle, the restriction member is displaced according to the movement of the inertial mass body to thereby restrict rotation of the V gear. If the lock base rotates in the state that the rotation of the V gear is restricted, relative rotation is caused between the V gear and the lock base, and the V gear displaces the lock plate due to the relative rotation, to thereby mesh the external teeth of the lock plate with the internal ratchet teeth. Thereby, the rotation of the lock base in the pulling-out direction is resisted. At this time, the webbing tensile force operates on the torsion shaft as a rotation force in the pulling-out direction via the take-up shaft. Thereby, the torsion shaft is distorted, and the take-up shaft is rotated in the direction for pulling out the webbing with respect to the lock base to thereby pull out the webbing. Hence, the energy is absorbed.
According to the webbing retractor of the fourteenth aspect, the urging means is the spiral coil spring. The one end of the spiral coil spring is engaged directly or indirectly with the take-up shaft, and the other end is directly or indirectly engaged with the other leg plate of the frame. When the take-up shaft is rotated in the pulling-out direction, the spiral coil spring is provided with increased number of winding, to thereby increase the restoring force. This restoring force becomes the urging force for urging the take-up shaft in the take-up direction.
According to the webbing retractor of the fifteenth aspect, the protrusions are formed in the opposite side of the rack bar with respect to the pinion, and on the inner peripheral portion of the bearing portion facing the outer peripheral portion of the shaft portion along the direction of the meshing face of the rack bar and the pinion.
The rack bar is to rotate the pinion by pressing the pinion teeth by means of the teeth of the rack bar, and the pressing force at this time operates in the direction of the meshing face between the rack bar and the pinion. Therefore, by forming the protrusions as described above, the number of the protrusions formed is greater in the eccentric direction of the pinion. Therefore, when the pinion becomes eccentric, the outer peripheral portion thereof arranged on the inside of the bearing means presses the protrusions to plastically deform them.
According to the webbing retractor of the sixteenth aspect, since the protrusion is brought into linear contact with the side where the protrusion is not formed, the pressing force concentrates more effectively on the protrusion. Hence, the protrusion is plastically deformed more easily.
According to the webbing retractor of the seventeenth aspect, when the inertial mass body moves due to change in the acceleration in the abrupt deceleration state of the vehicle, the restriction member is displaced according to the movement of the inertial mass body to thereby restrict rotation of the V gear. If the lock base rotates in the state that the rotation of the V gear is restricted, relative rotation is caused between the V gear and the lock base, and the V gear displaces the lock plate due to the relative rotation, to thereby mesh the external teeth of the lock plate with the internal ratchet teeth. Thereby, the rotation of the lock base in the pulling-out direction is resisted. At this time, the webbing tensile force operates on the torsion shaft as a rotation force in the pulling-out direction via the take-up shaft. Thereby, the torsion shaft is distorted, and the take-up shaft is rotated in the direction for pulling out the webbing with respect to the lock base to thereby pull out the webbing. Hence, the energy is absorbed.
According to the webbing retractor of the eighteenth aspect, the urging means is the spiral coil spring. The one end of the spiral coil spring is engaged directly or indirectly with the take-up shaft, and the other end is directly or indirectly engaged with the other leg plate of the frame. When the take-up shaft is rotated in the pulling-out direction, the spiral coil spring is provided with increased number of winding, to thereby increase the restoring force. This restoring force becomes the urging force for urging the take-up shaft in the take-up direction.
According to the webbing retractor of the nineteenth aspect, since the protrusion is brought into linear contact with the side where the protrusion is not formed, the pressing force concentrates more effectively on the protrusion. Hence, the protrusion is plastically deformed more easily.
According to the webbing retractor of the twentieth aspect, when the inertial mass body moves due to change in the acceleration in the abrupt deceleration state of the vehicle, the restriction member is displaced according to the movement of the inertial mass body to thereby restrict rotation of the V gear. If the lock base rotates in the state that the rotation of the V gear is restricted, relative rotation is caused between the V gear and the lock base, and the V gear displaces the lock plate due to the relative rotation, to thereby mesh the external teeth of the lock plate with the internal ratchet teeth. Thereby, the rotation of the lock base in the pulling-out direction is resisted. At this time, the webbing tensile force operates on the torsion shaft as a rotation force in the pulling-out direction via the take-up shaft. Thereby, the torsion shaft is distorted, and the take-up shaft is rotated in the direction for pulling out the webbing with respect to the lock base to thereby pull out the webbing. Hence, the energy is absorbed.
According to the webbing retractor of the twenty-first aspect, the urging means is the spiral coil spring. The one end of the spiral coil spring is engaged directly or indirectly with the take-up shaft, and the other end is directly or indirectly engaged with the other leg plate of the frame. When the take-up shaft is rotated in the pulling-out direction, the spiral coil spring is provided with increased number of winding, to thereby increase the restoring force. This restoring force becomes the urging force for urging the take-up shaft in the take-up direction.
According to the webbing retractor of the twenty-second aspect, when the inertial mass body moves due to change in the acceleration in the abrupt deceleration state of the vehicle, the restriction member is displaced according to the movement of the inertial mass body to thereby restrict rotation of the V gear. If the lock base rotates in the state that the rotation of the V gear is restricted, relative rotation is caused between the V gear and the lock base, and the V gear displaces the lock plate due to the relative rotation, to thereby mesh the external teeth of the lock plate with the internal ratchet teeth. Thereby, the rotation of the lock base in the pulling-out direction is resisted. At this time, the webbing tensile force operates on the torsion shaft as a rotation force in the pulling-out direction via the take-up shaft. Thereby, the torsion shaft is distorted, and the take-up shaft is rotated in the direction for pulling out the webbing with respect to the lock base to thereby pull out the webbing. Hence, the energy is absorbed.
According to the webbing retractor of the twenty-third aspect, the urging means is the spiral coil spring. The one end of the spiral coil spring is engaged directly or indirectly with the take-up shaft, and the other end is directly or indirectly engaged with the other leg plate of the frame. When the take-up shaft is rotated in the pulling-out direction, the spiral coil spring is provided with increased number of winding, to thereby increase the restoring force. This restoring force becomes the urging force for urging the take-up shaft in the take-up direction.
According to the webbing retractor of the twenty-fourth aspect, the urging means is the spiral coil spring. The one end of the spiral coil spring is engaged directly or indirectly with the take-up shaft, and the other end is directly or indirectly engaged with the other leg plate of the frame. When the take-up shaft is rotated in the pullindg-out direction, the spiral coil spring is provided with increased number of winding, to thereby increase the restoring force. This restoring force becomes the urging force for urging the take-up shaft in the take-up direction.